Massive freshwater reservoir discovered beneath Atlantic Ocean

Columbia University scientists used an electromagnetic receiver to study offshore groundwater deposits beneath the Atlantic Ocean. They discovered a vast freshwater reservoir extending from New Jersey to Massachusetts, starting 600 feet below the ocean floor. This reservoir likely formed at the end of the last Ice Age when lower sea levels exposed the continental shelf, allowing river deltas to trap freshwater. The aquifer is dynamic, fed by subterranean runoff, and shows a gradient from fresh to salty water as it mixes with the ocean.

How deep does the freshwater reservoir begin below the ocean floor?

What happens to the salinity of the water as one moves farther from the shore?